The invention relates to a vehicle seat with a head rest arranged on the back rest, having a supporting surface which the head of the vehicle occupant can touch for helping to protect the vehicle occupant.
A conventional head rest, in the case of a rear impact, helps protect the head of a vehicle occupant. Usually, head rests are able to be inserted into the back rest, are vertically adjustable and are adjustable towards the head of the vehicle occupant. An optimal initial position of the head rest, adapted to the position of the head, is to have a minimal distance from the head to the head rest.
The conventional head rest moves closer to the head of the occupant to help protect the vehicle occupant. Nevertheless, with too low or too high an arrangement of the head rest, it is not possible to support the head of the occupant in an optimal manner.
It is an object of the invention to provide a vehicle seat with a head rest which supports the head of a vehicle occupant irrespective of whether the head rest is optimally adjusted. This object is achieved in a vehicle seat of the present invention in that the head rest has an expansion device which increases the size of the supporting surface of the head rest for helping to protect the vehicle occupant. In addition, the head rest is vertically adjusted in relation to the back rest at least when the head rest is arranged so close to the back rest that the back rest would prevent a complete increase in size of the supporting surface. In accordance with the present invention, the supporting surface of the head rest is increased in size by means of the expansion device, so that in every initial position of the head rest the head of the occupant is supported equally well. A vertical adjusting device has the effect that the increased supporting surface is actually fully available because it may otherwise happen that the back rest so obstructs the expansion process that the size of the supporting surface is increased incompletely or with a delay in time.
The head rest is preferably moved into a predefined basic position in which the supporting surface extends upwards from close to the back rest and offers an optimal protective effect for occupants of differing sizes, irrespective of the initial position of the head rest. In this position the back rest does not obstruct the enlargement process of the supporting surface. In addition, the head rest may be supported on the back rest and thereby move into the basic position itself by means of an increase in volume if the back rest prevents a complete increase in the size of the supporting surface with the head rest being set too close to the back rest.
The invention may be realized in two embodiments. According to the first embodiment, the supporting surface is achieved by inflating a gas bag. In the second embodiment, the expansion device is a mechanical device by means of which the supporting surface is increased, for example by the swivelling of levers or by moving apart individual padding elements of the head rest. In each of these embodiments, the head rest can, in addition, be actively moved closer to the head of the occupant for helping protect the vehicle occupant.